I am assuming that it is quoting a price + GST is ok, as several operators up here do it. Gotta be careful, I cross hired a plane and assumed it was GST inclusive... until the bill........
Frankly I cannot see the point why not just advertise your price? Your client doesn't have to be Einstein to work out the GST component if they are to lazy to look at the invoice.
Must say though i'm not sure on the legislation as we include GST...